Known in the art are some surgical instruments for applying staple or multistaple sutures (cf., e.g., U.S. Pat. No. 3,315,863). These instruments include a frame shaped as a hook with a jaw carrying a die provided with recesses for the staples to bend, a staple head, a magazine with slots for staples, a staple ejector and mechanical actuators of the staple head and ejector. The instruments, however, are disadvantageous in having not adequately rigid construction of the frame shaped as a hook, which results in deformation of the hook and an inadmissible change in the magazine-to-die distance due to heavy loads imposed upon the instrument when applying lengthy multistaple sutures (which is the case when stitching up the stomach with a double-row suture 100 to 150 mm long). As a result, the proper mutual arrangement of the die recesses and the respective magazine slots is affected, whereby the staples fail to be bent tightly enough, the obtained suture is insufficiently hermetic, and hemostasis thus occurs. In order to increase rigidity of the frame and obtain a high-quality staunch suture, the cross-sectional dimensions of the frame elements are considerably increased, which adds to the weight of the instrument as a whole, a feature that affects adversely manipulations with the instrument within a restricted area of the operative field and the functional capabilities of the instrument, results in obtaining too a rough suture due to abnormally increased distance from the suture to the cut of the tissues.
The above-mentioned disadvantages are to a great extent eliminated in another instrument for suturing human organs, according to U.S. Pat. No. 3,494,533. Said instrument comprises a body with a closed rectangular frame adapted to interact with a staple head, comprising a staple magazine and an ejector, each of these having a mechanical actuator.
The frame consists of a .andgate.-shaped member one of whose legs carries a die, and a detachable rod, which interlinks the legs of the .andgate.-shaped member. The functional expediency of the construction of said instrument consists in that the closed frame may be opened aside of the die-carrying leg, whereby the instrument can be conveniently brought to the organ being sutured, e.g., in the case of the stomach resection.
Said instrument has a number of disadvantages, the principal of which is that the frame construction fails to provide an ample rigidity for the stitching mechanism, which undergoes heavy loads applied in three mutually square directions when suturing tissues or organs. In addition, the frame of the instrument is too complicated, inconvenient and short-lived.
The above-mentioned disadvantages stem from the construction of the frame in the known instrument. Thus, the detachable rod of the frame is a cylinder-shaped, having a thread at one end and a head at the other. The rod is joined with the legs of the .andgate.-shaped member through a threaded hole in the die-carrying leg and through an additional intermediate sleeve having an external thread and adapted to be screwed into the threaded hole provided in the end of the other end of the .andgate.-shaped frame member. The detachable cylindrical rod is fitted in to the hole in the intermediate sleeve and screwed into the threaded hole in the die-carrying leg.
Inasmuch as the cylindrical rod serves also for locking in position the detachable staple magazine and and the discardable die, said rod runs through special centering holes in the magazine and die and hence has its cross-sectional diameter much less than the width of the magazine located in the staple head, and of the die. On the other hand, the cylindrical rod surface and the centering holes in the magazine and die should be accurately gauged to provide a required fitting accuracy, so that the thread on the rod end has still lesser diameter than the diameter of the rod gauged portion.
It is quite obvious that such a construction of the detachable rod, which is in fact one of the lateral sides of the closed frame, features much lower tensile rigidity and transverse rigidity in the plane of the frame and normally thereto than the rigidity of the other lateral side, which interlinks the legs of the .andgate.-shaped member as a permanent joint and which does not run through out the magazine and die. Besides, hinged joint of the cylindrical rod with the legs of the .andgate.-shaped frame member, the magazine and the die fails to compensate for twisting moments resulting from a transverse flexure of said components in the plane normal to the plane of the frame.
Great forces are applied to the stitching mechanism of the instrument in the course of compressing the tissues being sutured and performing a once-through deformation of a large number of staples; thus, for instance, the forces applied to the stitching mechanism when placing a double-row 100 to 150 mm long suture with staple made of a dia. 0.3 mm wire, amount to 100 or 140 kgf. It is due to low rigidity of the whole construction and on account of a hinged joint of the cylindrical rod with the legs of the .andgate.-shaped frame member, the magazine and the die, that the magazine-to-die clearance is increased in the direction of suturing, the magazine and the die are mutually dislodged in the plane of the frame and in a direction normal to the abovesaid plane. This leads to an axial misalignment of the staple recesses and the staple slots, an inadequately tight staple bending after the suturing and its distorted shape (asymmetrical bending) and hence to a nonstaunt suture, affected suture tightness and hemostasis.
Low rigidity of the detachable rod resulting from the frame construction, eventuates in an inadmissible deformation of the rod. As it is stated in the description of the instrument according to U.S. Pat. No. 3,494,533 (column 14, line 74), the rod must be discarded after use as having been subjected to bending forces and thus being liable to deform, thereby upsetting the central alignment of the magazine and die if reused. That is why the detachable cylindrical rod applied in said instrument is to be made discardable so that a fresh rod must be available for every next suturing operation, which is economically inexpedient.
Low durability of the cylindrical rod and its being unsuitable for multiple use is also due to the fact that small-diameter thread has to be made use of in the construction of the known instrument, which is subject to substantial wear and deformation upon multiple repeated screwing in and out, which is liable to cause abnormal plays in the threaded joint. In addition, such a rod is practically inapplicable in small-sized instruments adapted for use in, say, preschool children, since in this case the thread diameter should be still smaller and such a thread cannot be used a heavy-duty one.
In order to compensate for said disadvantages in the construction of the known instrument manifested themselves under heavy loads applied to the stitching mechanism thereof, one must increase the rigidity of the structural members of said mechanism by increasing the cross-sectional dimensions of the legs and of the lateral (with respect to the legs) side of the .andgate.-shaped frame member, as well as of the cylindrical rod. This, however, will render the instrument more bulky and will lead to a wider space between the suture staples and the cut of the tissues being sutured, performed along the leg of the .andgate.-shaped frame member, on account of which the obtained suture will be still more rough and be featured by a large tissue torus.
Complexity of the construction of the known instrument and its being inconvenient for use are accounted for by the fact that the detachable cylindrical rod of the frame must involve, for being linked to the free ends of the legs of the .andgate.-shaped member, one more intermediate piece made as a sleeve provided between the rod and one of the legs of the .andgate.-shaped frame member. Thus, the abovesaid sleeve is to be first made fast on the leg, than the cylindrical rod is to be fitted into a number of holes in the sleeve, magazine, die and die-carrying leg, which should be brought in strict register with one another. This done, one must give the rod several turns. The rod end has a tapered surface which, when the rod is being set to working position, presses as a cam upon a special projection in the centring hole of the magazine and upon the cylindrical face of the hole in the die.
One more inconvenient feature of the known instrument resides also in the fact that the magazine and die can be replaced not until the cylindrical rod is taken apart and completely removed from the instrument, and the instrument itself is taken out of the operative wound. The instrument cannot be applied repeatedly unless a new set of magazine, die and rod is available and these components are set to their respective working position. This place a limitation upon the functional capabilities of the instrument, in particular, prevents its convenient use, without removing the instrument from the operative wound, for applying two parallel sutures to the organ, accompanied by severing the tissues between the sutures with a scalpel, which proves to be expedient when applying sutures to the remaining stump of the organ operated upon, and to its ablated portion, e.g., when stitching up the stomach, or for establishing a tube from the walls of the greater curvature of the stomach in the case of esophagoplasty.
In addition, the intermediate sleeve and small-diameter threaded hole in the leg of the .andgate.-shaped frame member are inconvenient cleansing.